Broadband wave plates made by plasmonic metamaterials

Lin Chen,Lei Zhou,Xun Li,Huijie Guo,Junhao Li,Xianmin Ke

doi:10.1038/s41598-018-19611-8

Abstract

Although metamaterials wave-plates have been demonstrated previously, many of them suffer from the issue of narrow bandwidth since they typically rely on resonance principles and thus exhibit inevitable frequency dispersions. Here, we show that the dispersion of spoof surface plasmon (SSP) mode supported by a fishbone structure can be freely modulated by varying the structural parameters. This motivates us to establish a general strategy of building broadband wave-plates by cascading two fishbone structures with different propagation constants of SSP modes. We derive a criterion under which the cross-polarization phase-difference across the whole device can maintain at a nearly constant value over a wide frequency band, with frequency dispersions in the two fishbone structures cancelled out. As an illustration, we design and fabricate an efficient microwave quarter-wave plate and experimentally characterize its excellent polarization-control performances over a broad frequency band (7–9.2 GHz). Our findings can stimulate making dispersion-controlled high-performance optical functional devices in different frequency domains.

Highlights

Metamaterials wave-plates have been demonstrated previously, many of them suffer from the issue of narrow bandwidth since they typically rely on resonance principles and exhibit inevitable frequency dispersions
Previous study has demonstrated that a single fishbone structure array supporting spoof surface plasmon (SSP) modes fails to construct a broadband wave plate since the cross-polarization phase difference could not be kept constant within a wide spectral band[30,31]
We proposed a general strategy for designing transmission-mode broadband wave-plates by integrating two fishbone structures with sides walls decorated with different plasmonic metamaterials

Summary

Introduction

Metamaterials wave-plates have been demonstrated previously, many of them suffer from the issue of narrow bandwidth since they typically rely on resonance principles and exhibit inevitable frequency dispersions. We show that the dispersion of spoof surface plasmon (SSP) mode supported by a fishbone structure can be freely modulated by varying the structural parameters This motivates us to establish a general strategy of building broadband wave-plates by cascading two fishbone structures with different propagation constants of SSP modes. We establish a general strategy to build high-performance broadband wave-plates based on spoof surface plasmon (SSP) modes with phase dispersions well controlled. Previous study has demonstrated that a single fishbone structure array supporting SSP modes fails to construct a broadband wave plate since the cross-polarization phase difference could not be kept constant within a wide spectral band[30,31]. Our results, based on a general dispersion-control strategy, can inspire making broadband transmission-mode optical devices with other functionalities, such as half-wave plate, and in different frequency domains

Methods

Results

Conclusion